Chris Pratt tells Conan O’Brien how he went from flabby to fit to flabby again

When looking at "before" and "after" weight-loss photos, the subject usually goes from chubby to chiseled. But as actor Chris Pratt proved while appearing on "Conan" with Conan O'Brien, that's not always the case.

"I don't know if you could tell from the angle right now, but I'm kind of like a fat-ass," the 33-year-old "Parks and Recreation" star told O'Brien. "I have a bit of extra belly going on. I've always been a little soft, and I like to eat, and crunches I'm not going to do."

But for Pratt's new Oscar-buzzed movie "Zero Dark Thirty," in which he plays a SEAL Team 6 member on the hunt for Osama Bin Laden, the actor had to do some serious training.

"I had about five or six months to really bust my ass and get in good shape," Pratt said, and then shared evidence of the results: a self-taken photo of Pratt in the bathroom mirror barely recognizable in a pair of tighty-whities, flexing his rock-hard abs and bulging muscles.

"And then after I wrapped the movie, I almost immediately gained like 60 pounds to play a role in another movie," Pratt admitted. The picture he brought along for that showed much less of Pratt's bare chest, and much more of his double chin.

In that film, "Movie 43," Pratt plays "a kind of despondent, emasculated character that's fat and unhappy." The film has a huge ensemble cast, featuring Elizabeth Banks, Justin Long, Naomi Watts, Uma Thurman, Kristen Bell, and Pratt's wife, Anna Faris. The comedic couple were married in 2009 and had their first child, Jack, on Aug. 25, 2012.

Faris, too, has experience some body changes since going through pregnancy. But much like her husband, the 36-year-old "Scary Movie" actress isn't in a rush to get back to the gym. And Pratt is more than supportive of her decision to keep her curves.

"He makes me feel good at any weight. In fact, I kinda think that he likes it when my butt is a little bit bigger," Faris told E! News earlier this month.